"Manafort is a key person to help us unwind whether this is the most unlikely string of improbable coincidences or whether this is an active conspiracy", said California Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee.

Prosecutor Andrew Weissman said in court on Friday that Manafort had struck a "cooperation agreement".

After Manafort was convicted in the August case, Trump said he had "such respect for a fearless man: because "he refused to "break" - make up stories in order to get a 'deal'". "He's accepted responsibility. This is for conduct that dates back many years and everybody should remember that", Manafort's attorney, Kevin Downing, said.

"You see people recognising they don't trust the president".

Trump's former campaign manager has made a decision to work with investigators.

Brock Long, the administrator of FEMA, echoed Trump's statements disputing the death toll in Puerto Rico a year ago on Meet The Press today, going so far as to claim some of the hurricane-related deaths may be incidents of "spousal abuse". He's on to him. "So it is a very significant breakthrough", Starr told ABC News.

Though Donald Trump has repeatedly denied that he colluded with Russia, Paul Manafort could have information about one of the most damaging incidents during the 2016 presidential campaign - a meeting at Trump Tower with a Kremlin-connected lawyer offering dirt on Hillary Clinton that had been stolen by Russian hackers.

U.S. President Donald Trump claimed Sunday, without evidence, that the ongoing criminal investigation into his 2016 campaign's links to Russian Federation is "not allowed under the law".

Experts pointed out that the plea deal explicitly says that "no agreements, promises, promises, or representations" were made outside of what is contained within that September 14 written agreement. Scott Dworkin, a Democratic strategist and MSNBC contributor, said he believes that Trump will resign within two weeks now that Manafort has turned.

"The decision by Manafort to provide evidence in exchange for leniency on sentencing is a stunning development in the long-running probe into whether any Trump associates may have conspired with Russian Federation to influence the 2016 election", reported The Washington Post. Mueller has already secured cooperation from a former national security adviser who lied to the Federal Bureau of Investigation about discussing sanctions with a Russian ambassador, a campaign aide who broached the idea of a meeting with Russian President Vladimir Putin; and another aide who was indicted alongside Manafort but ultimately turned on him. "There are no limits".

But Harvard law professor emeritus Alan Dershowitz said Giuliani is putting a positive spin on "bad" situation for President Trump.

All of which is to say that this has been an extremely fruitful special counsel investigation already.

Though it's unclear how the deal could affect any pursuit by Manafort of a pardon from Trump, Dershowitz said it's "too late" for that. "I don't think - given the nature of the fight that Manafort put up, the seriousness of the crimes, and the power of the evidence of those crimes, Jon - that this deal would have been offered absent some very powerful evidence".

He said that with "the best ever" economy, his poll numbers "would be 25 points higher" if not for the "highly conflicted Bob Mueller" and his investigation.

The White House has said that Papadopoulos was a low-level volunteer on the campaign.